Years Of Monthly Observations Research Articles

Disentangling environmental effects in microbial association networks

BackgroundEcological interactions among microorganisms are fundamental for ecosystem function, yet they are mostly unknown or poorly understood. High-throughput-omics can indicate microbial interactions through associations across time and space, which can be represented as association networks. Associations could result from either ecological interactions between microorganisms, or from environmental selection, where the association is environmentally driven. Therefore, before downstream analysis and interpretation, we need to distinguish the nature of the association, particularly if it is due to environmental selection or not.ResultsWe present EnDED (environmentally driven edge detection), an implementation of four approaches as well as their combination to predict which links between microorganisms in an association network are environmentally driven. The four approaches are sign pattern, overlap, interaction information, and data processing inequality. We tested EnDED on networks from simulated data of 50 microorganisms. The networks contained on average 50 nodes and 1087 edges, of which 60 were true interactions but 1026 false associations (i.e., environmentally driven or due to chance). Applying each method individually, we detected a moderate to high number of environmentally driven edges—87% sign pattern and overlap, 67% interaction information, and 44% data processing inequality. Combining these methods in an intersection approach resulted in retaining more interactions, both true and false (32% of environmentally driven associations). After validation with the simulated datasets, we applied EnDED on a marine microbial network inferred from 10 years of monthly observations of microbial-plankton abundance. The intersection combination predicted that 8.3% of the associations were environmentally driven, while individual methods predicted 24.8% (data processing inequality), 25.7% (interaction information), and up to 84.6% (sign pattern as well as overlap). The fraction of environmentally driven edges among negative microbial associations in the real network increased rapidly with the number of environmental factors.ConclusionsTo reach accurate hypotheses about ecological interactions, it is important to determine, quantify, and remove environmentally driven associations in marine microbial association networks. For that, EnDED offers up to four individual methods as well as their combination. However, especially for the intersection combination, we suggest using EnDED with other strategies to reduce the number of false associations and consequently the number of potential interaction hypotheses.39dy5mFVH5LkqSifW2AWwCVideo abstract

Uso de metodologias de preenchimento de falhas para estimativas de dados de precipitação

No presente trabalho, as metodologias para preenchimento de falhas em séries temporais de precipitação foram utilizadas, não como ferramenta auxiliar no preenchimento de lacunas provocadas por erros, mas sim como um meio de prever integralmente os dados de pluviometria para o município de Catanduva, baseando-se em dados dos municípios de São Carlos (SC), Franca (FR) e Votuporanga (VT), localizados no estado de São Paulo. Objetivando assim, analisar e avaliar a viabilidade do uso dos métodos da ponderação regional, da regressão linear simples e da regressão linear múltipla, verificando o desempenho e a correlação entre os dados estimados e os dados reais (registrados pelo posto pluviométrico de Catanduva). Foram utilizadas informações de séries históricas com 30 anos de observações mensais fornecidas pelo Instituto Nacional de Meteorologia (INMET) para a aplicação dos métodos citados. Comparando os dados estimados aos dados medidos pode-se afirmar que o método da regressão linear múltipla foi o que melhor simulou a realidade dos eventos observados e que as estimativas têm melhor desempenho para os meses menos chuvosos e quando são utilizados dados pluviométricos de regiões próximas.

Biodiversity of epifauna in the ports of Southern Baltic Sea revealed by study of recruitment and succession on artificial panels

Ports are highly dynamic environments that are under substantial anthropogenic pressure generated by activities related to the fishery, transhipment of cargo and passenger traffic. Thus, seaports are exposed to physical disturbances, chemical pollution and biological invasions. Yet knowledge about biotic part and the influence of anthropogenic pressure on it in seaports often does not exist. The main aim of this study was to assess the biodiversity of the hard-bottom epifauna by examination of the course of the recruitment and succession processes in the poorly known port basin ecosystem of the southern Baltic Sea at the ports of Gdańsk, Gdynia and Władysławowo. We wanted to test whether the different port areas had their unique species diversity and compositions. In all investigated ports we found relatively low biodiversity but high recruitment activity of sessile fauna. Six epifaunal species were observed, and Amphibalanus improvisus was consistently the dominant species (up to 47,126.5 ± 2747.1 SD individuals per 225 cm2 in July in Gdynia port). Seasonality was found to be the main factor shaping recruitment and further development of the sessile assemblages, and the seasonal sequences of epifaunal occurrence were similar in the three examined ports. Furthermore, the epifauna of all ports showed homogenous species richness, composition and abiotic characteristics, although in the Władysławowo port, which is more exposed to the open sea, a higher abundance of meroplankton and greater shares of accessory species (Mytilus spp., Limecola balthica, Cerastoderma glaucum and Mya arenaria) were found. The assemblage structures of the ports resembled those of nearby natural system (Gulf of Gdańsk); thus, the port ecosystem seems to be an integral part of the surrounding natural habitat. Two years of monthly observations did not reveal any new non-native species in the examined study area.

Modeling sediment diagenesis processes on riverbed to better quantify aquatic carbon fluxes and stocks in a small watershed of the Mid-Atlantic region

BackgroundDespite the widely recognized importance of aquatic processes for bridging gaps in the global carbon cycle, there is still a lack of understanding of the role of riverbed processes for carbon flows and stocks in aquatic environments. Here, we added a sediment diagenesis and sediment carbon (C) resuspension module into the SWAT-C model and tested it for simulating both particulate organic C (POC) and dissolved organic C (DOC) fluxes using 4 years of monthly observations (2014–2017) in the Tuckahoe watershed (TW) in the U.S. Mid-Atlantic region.ResultsSensitivity analyses show that parameters that regulate POC deposition in river networks are more sensitive than those that determine C resuspension from sediments. Further analyses indicate that allochthonous contributions to POC and DOC are about 36.6 and 46 kgC ha−1 year−1, respectively, while autochthonous contributions are less than 0.72 kgC ha−1 year−1 for both POC and DOC (less than 2% of allochthonous sources). The net deposition of POC on the riverbed (i.e., 11.4 kgC ha−1 year−1) retained ca. 31% of terrestrial inputs of POC. In addition, average annual buried C was 0.34 kgC ha−1 year−1, accounting for only 1% of terrestrial POC inputs or 3% of net POC deposition. The results indicate that about 79% of deposited organic C was converted to inorganic C (CH4 and CO2) in the sediment and eventually released into the overlying water column.ConclusionThis study serves as an exploratory study on estimation of C fluxes from terrestrial to aquatic environments at the watershed scale. We demonstrated capabilities of the SWAT-C model to simulate C cycling from uplands to riverine ecosystems and estimated C sinks and sources in aquatic environments. Overall, the results highlight the importance of including carbon cycle dynamics within the riverbed in order to accurately estimate aquatic carbon fluxes and stocks. The new capabilities of SWAT-C are expected to serve as a useful tool to account for those processes in watershed C balance assessment.

Synchronous species responses reveal phenological guilds: implications for management

AbstractPhenological studies are critical for understanding the ability of terrestrial ecosystems to respond to changes in climate. Monitoring seasonal transitions at the species or community level across large areas is challenging and expensive. One approach for lowering costs is to identify phenological guilds—groups of species that exhibit similar timing of seasonal transitions—and limit monitoring to a smaller number of species within a guild. In this study, we evaluated 23 consecutive years of monthly observations of individual species at 15 long‐term study sites at the Jornada Basin USDA‐Long‐Term Ecological Research site to identify patterns in the onset of three phenophases—leaf‐out, flower, and fruit—of 16 widely occurring species in the arid southwestern United States and to investigate the existence of phenological guilds. We conducted univariate analyses of distributions in the timing of leaf, flower, and fruit production across time and space and multivariate cluster analysis of the time series to identify coherent groups of species–site instances that exhibit coherence in timing of phenophase onsets (i.e., guilds). The six species of C3 shrubs demonstrated greater consistency in timing of all phenophases relative to C4 grasses. Further, we found that in all species, leaf‐out occurred prior to the onset of the summer monsoon rains. Cluster analysis revealed six groups of species–site observations demonstrating high within‐year concordance in timing of leaf‐out and first fruit across variable site conditions and rainfall years. The six groups for timing of first fruit differed from those for first leaf in that they exhibited greater multi‐species membership and within‐year variability in timing. We propose that use of phenological guilds can improve the efficiency of ecosystem monitoring, predictive models of ecosystem cues driving phenological events, and land management outcomes.

Losses Loom Longer than Gains: Modeling the Impact of Service Crises on Perceived Service Quality over Time

Service providers sometimes face mass service failures. These problems occur across service industries, ranging from severe Internet outages to major delays for airlines or trains. The literature has not yet addressed the following key question: How do service crises affect perceived service quality (PSQ) over time? To answer this question, the authors introduce a Double-Asymmetric Structural Vector Autoregressive model. It captures not only the short- and long-term effects of objective service performance on PSQ but also the differential effects of service crises versus service restoration. The authors analyze a unique data set from a major European railway company, spanning seven years of monthly observations. During this period, severe winter weather caused dramatic service crises. The authors find that performance losses loom larger than gains in the short run and also have permanent negative effects on PSQ in the long run. Consequently, a crisis followed by a restoration will result in a net negative long-term effect on PSQ. The impact of a crisis also depends on the prior trend in objective service performance.

Historical pan evaporation changes in the Qiantang River Basin, East China

Pan evaporation (Epa) has been decreasing in many regions of the world in the past decades. Analysis of the changes in Epa helps to understand the variation of vapour in the hydrological cycle and the impact of climate change on Epa. This study aims to investigate the spatial and temporal trends in Epa and analyse the causes of Epa variation in the Qiantang River Basin, East China. A self-organizing map neural network is first applied to classify the 40 hydrological stations. Based on the clustering results, a trend-free pre-whitening Mann–Kendall test is then used to investigate the historical trends in Epa based on more than 50 years of monthly observations. Finally, sensitivity analysis is conducted for evaluating the relationship between Epa and five climate variables and for investigating the causes of changes in Epa using a global, variance-based method. It is found that the hydrological stations located in this basin can be classified into six sub-areas and the Epa trends vary substantially at six sub-areas. Generally, there is a decreasing trend of Epa in a majority of months in all sub-areas except one and the most significant decreases occur in summer. The results of sensitivity analysis reveal that Epa is more sensitive to solar radiation, followed by minimum air temperature, wind speed, relative humidity and maximum air temperature. The contribution of interactions between different climate variables to the variation of Epa cannot be ignored in some specific stations. Overall, the change of Epa is mainly due to the decrease of solar radiation. This study provides an in-depth understanding of the causes of Epa variation and valuable information for sustainable water and crop management in this region.

Probabilistic Seasonal Prediction of Meteorological Drought Using the Bootstrap and Multivariate Information

AbstractIn the present work, a probabilistic ensemble method using the bootstrap is developed to predict the future state of the standard precipitation index (SPI) commonly used for drought monitoring. The methodology is data driven and has the advantage of being easily extended to use more than one variable as predictors. Using 110 years of monthly observations of precipitaton, surface air temperature, and the Niño-3.4 index, the method was employed to assess the impact of the different variables in enhancing the prediction skill. A predictive probability density function (PDF) is produced for future 6-month SPI, and a log-likelihood skill score is used to cross compare various combination scenarios using the entire predictive PDF and with reference to the observed values set aside for validation. The results suggest that the multivariate prediction using complementary information from 3- and 6-month SPI and initial surface air temperature significantly improves seasonal prediction skills for capturing drought severity and delineation of drought areas based on observed 6-month SPI. The improvement is observed across all seasons and regions over the continental United States relative to other prediction scenarios that ignore the surface air temperature information.

New evidence from the random walk hypothesis for BRICS stock indices: a wavelet unit root test approach

We examine the use of the random walk hypothesis on the BRICS stock indices. Our examination of the stock indices uses a recently developed wavelet-based unit root test by Fan and Gençay (2010) along with a battery of unit root tests. We also examine the sensitivity of the wavelet-based unit root test. Our wavelet-based unit root tests show evidence that rejects the null of the unit root for all of the BRICS countries except for the Russian Federation. Hence, the tests provide support for the predictability of stock market indices in these economies on the basis of historical information. However, there is a need for caution because the results are based on a relatively small sample of only 11years of monthly observations.

Stock return outliers and beta estimation: The case of U.S. pharmaceutical companies

Efficient estimation of the equity cost of operating public corporations is essential for a rational investment policy. Traditional OLS beta estimates of a single stock are known to suffer from violations of normality due to outliers – extreme returns caused by large, unpredictable company-specific events. We confirm the presence of an outliers-driven, often significant bias in OLS beta estimates by undertaking parallel estimates with a related method based on a mixed-return model that follows Huber's Robust M (HRM) estimator. We demonstrate that the OLS bias can be substantial even in a sample spanning 18 years of monthly observations.

Sources of δ15N variability in sinking particulate nitrogen in the Cariaco Basin, Venezuela

Ten years of monthly observations of the δ15N of sinking particulate nitrogen (δ15N–PN (in ‰ versus atmospheric N2)=[(15N/14N)sample/(15N/14N)standard)−1]1000) in the Cariaco Basin, Venezuela, confirm that the basin's bottom sediments store information about nitrogen dynamics related to seasonal and interannual variability in regional surface ocean processes. During the upwelling period of the southern Caribbean Sea (February–April), the δ15N–PN is similar to that of the thermocline nitrate (∼3.5‰). This nitrate is imported into the Cariaco Basin with Subtropical Underwater (SUW), which wells up near the coast. Thus, particles generated by phytoplankton photosynthesis during this productive period bear a sub-tropical North Atlantic isotopic imprint of N2 fixation (low compared to the global average of nitrate δ15N≈5‰). During the non-upwelling period when surface waters are stratified (September–November), the δ15N–PN is also 3.5–4.0‰, and reflects a mixture of local N2 fixation within the mixed layer, inputs of terrigenous organic matter and SUW nitrate consumption by phytoplankton below the mixed layer, which most likely exerts the strongest control on the δ15N–PN signal during this time. In the transition periods of May–July and December–January, the δ15N–PN increases to 4.5–6.5‰. This coincides with maxima of continental material fluxes (terrestrial PON δ15N is >6‰) into the Cariaco Basin. The δ15N signal in the sediments of the Cariaco Basin thus provides information about the relative strength of the local coastal upwelling, the relative input of continental material via river runoff, and local N2 fixation. The findings contribute to interpretations of the basin's paleoclimatic nitrogen cycle variations based on observations of the sedimentary δ15N record at this location.

Rainfall-Driven Amplification of Seasonal Acidification in Poorly Buffered Tropical Streams

Acidification in freshwater ecosystems has important ecological and biogeochemical effects. Temperate streams affected by anthropogenic acidification have been extensively studied, but our understanding of natural acidification in tropical streams has been constrained by the lack of long-term datasets. Here, we analyze 14 years of monthly observations from 13 sampling stations in eight tropical streams in lowland Costa Rica. Stream pH increased during the 4-month dry season and declined throughout the wet season. The magnitude of the seasonal pH decline was greatest following the driest dry seasons, including the historically large El Nino Southern Oscillation event in 1998 when pH values dropped below 4.0 in some streams. Dissolved CO2 accounts for the low baseline pH in the poorly buffered study streams, and we hypothesize that an influx of soil-derived CO2 via subsurface flow paths contributes to the observed seasonal pH declines. Our results show tight coupling between rainfall, terrestrial, and aquatic ecosystems in the tropics. Predicted decreases in dry season rainfall for the tropics may lead to an increased magnitude of seasonal acidification.

Equilibrium shoreline response: Observations and modeling

Shoreline location and incident wave energy, observed for almost 5 years at Torrey Pines beach, show seasonal fluctuations characteristic of southern California beaches. The shoreline location, defined as the cross‐shore position of the mean sea level contour, retreats by almost 40 m in response to energetic winter waves and gradually recovers during low‐energy summer waves. Hourly estimates of incident wave energy and weekly to monthly surveys of the shoreline location are used to develop and calibrate an equilibrium‐type shoreline change model. By hypothesis, the shoreline change rate depends on both the wave energy and the wave energy disequilibrium with the shoreline location. Using calibrated values of four model free parameters, observed and modeled shoreline location are well correlated at Torrey Pines and two additional survey sites. Model free parameters can be estimated with as little as 2 years of monthly observations or with about 5 years of ideally timed, biannual observations. Wave energy time series used to calibrate and test the model must resolve individual storms, and model performance is substantially degraded by using weekly to monthly averaged wave energy. Variations of free parameter values between sites may be associated with variations in sand grain size, sediment availability, and other factors. The model successfully reproduces shoreline location for time periods not used in tuning and can be used to predict beach response to past or hypothetical future wave climates. However, the model will fail when neglected geologic factors are important (e.g., underlying bedrock limits erosion or sand availability limits accretion).

A simple advection‐dispersion model for the salt distribution in linearly tapered estuaries

We present a simple advection‐dispersion model for the subtidal salt distribution in estuaries with linearly varying cross‐sectional area and a nonzero net salt flux. A novel analytic solution allows investigation of the dependence of the curvature and gradient of the longitudinal salinity distribution on runoff, dispersion coefficient, and channel contraction or expansion. The model predicts that in estuarine segments that contract toward the fresher boundary, the salinity gradient is stronger than in a prismatic channel. When the dispersion coefficient is large compared to the salinity intrusion lengthscale, (the product of segment length and net volume flux divided by cross‐sectional area at the ocean boundary), the curvature of the salt concentration may be negative, a characteristic not possible in uniform channel models. The main effect of up‐estuary salt flux is to strengthen the salinity gradient. The model can be extended to multiple segments in order to simulate geometrically complicated estuaries. The model is employed to estimate an effective dispersion coefficient and to describe the salinity variation in the western 53 km of Long Island Sound where the cross section of the basin varies linearly. Using 8 years of monthly observations at seven stations we find that, since the curvature of the vertically averaged salinity is negative, the model and data are consistent only if the net volume flux and salt flux are toward the fresher boundary, the East River. Combining prior estimates of the magnitudes of the fluxes and their uncertainties with the model and salinity observations using a least squares approach, we estimate the dispersion coefficient for the Western Sound as 580 m2/s.

An exploratory study of relative and incremental information content of two non-financial performance measures: Field study evidence on absence frequency and on-time delivery

In this exploratory field study, I test the relative and incremental information content of two non-financial performance measures compared to financial performance measures for future financial performance. The proprietary database used is from the contracts of the managers of 27 responsibility centers of a large Dutch service firm. Three years of monthly observations are used for the analysis. The accounting literature is ambiguous about whether non-financial measures have relative or incremental information content, or both, beyond lagged financial measures for future financial performance. Although it is often stated that non-financial performance measures are better indicators for future financial performance than lagged financial performance, the empirical accounting research evaluates the incremental contribution of non-financial measures beyond lagged financial measures. I find that in my research context the two non-financial measures absence frequency and on-time delivery do not have more relative information content than lagged financial measures. However, the non-financial measures have incremental information content beyond the lagged financial measures for both future costs and future revenues. In addition, the individual non-financial measures have different lags for costs and revenues.

Seasonal variation in water chemistry and depositional processes in a tufa-bearing stream in SW-Japan, based on 5 years of monthly observations

Annually laminated freshwater carbonate (tufa) is a potential source of high-resolution terrestrial paleoclimate data. In order to understand the processes and characteristics of climate information recorded in tufa, the chemical components of carbonate-rich water, its flow rate and soil P CO 2 were recorded monthly during a 5-year period (December 1997 to December 2002) at Shimokuraida (Niimi City, Okayama Prefecture), SW-Japan. Water issues from a limestone cave there flows along a 450-m long stream and deposits tufa that commonly exhibits distinct annual laminations. Among observed properties, the CO 2 partial pressures in the soil and the spring water show the clearest seasonal patterns, which are similarly high in summer–autumn and low in winter–spring. The spring-water P CO 2 partly reflects soil P CO 2 , but is controlled by another temperature-dependent process, natural ventilation between the subsurface and the atmosphere. The concentration of dissolved CaCO 3 does not mirror the seasonal pattern of spring-water P CO 2 , but is largely influenced by rainfall dilution. The development of annual laminations results from seasonal changes in the depositional rate of CaCO 3, which was faster from summer to autumn and slower from winter to spring. This seasonal pattern is initially controlled by relatively regular changes in water temperature and flow rate, both of which correlated positively with the calcite precipitation rate. High calcite precipitation in summer–autumn formed a densely calcified texture, whereas a precipitation low rate winter–spring formed a porous texture. Changes in the concentrations of minor dissolved components (Mg 2+, Na +, K +, Cl −, NO 3 −, SO 4 2− and SiO 2) exhibited no seasonal pattern. Because the amplitude of the Mg/Ca change is very high at Shimokuraida, the Mg/Ca ratio of tufa (calcite) does not reflect paleotemperatures. While, Mg/Ca ratio of water does not correspond to rainfall intensity, too.

How homogenous are currency crises? A panel study using multiple - response models

This paper presents formal evidence that currency episodes display heterogeneity in terms of their evolution, their impact on the inflicted economy and their links with financial, political and macroeconomic fundamentals. Limited-dependent variable models for ordered and unordered outcomes along with their heteroskedastic and random effects extensions are applied on a large panel of data comprising 40 years of monthly observations on 23 developed countries. Heterogeneity, complemented by indications of self-fulfilling expectations and noise, suggest that time and region specific predictive approaches and policy responses are more useful than trying to base analysis and policy decisions on more general patterns. Results are established with formal specification tests.

An analysis of the rainfall time structure by box counting—some practical implications

The scale-invariant behavior of the rainfall time structure was investigated by applying the box counting method to rainfall time series. Two years of minute observations, 90 years of daily observations and 170 years of monthly observations were analyzed and the results were interpreted and related to physical properties of the rainfall process. This paper discusses the question of whether an hypothesis of temporal scale invariance is valid for rainfall and the possibilities of using it in practical hydrology.

Goat herbivory and plant phenology in a Mediterranean shrubland of northern Baja California

Two years of monthly observations of the feeding behaviour of goats on the northern Baja California coastal shrubland, made by the bite-count method, indicate that eight shrub species, plus all herbs grouped in a single category, comprise about 80% of their diet, although 27 other species were consumed occasionally. Five phenological stages were detected in the plant communities throughout the year and an extremely close relationship was observed between them and the feeding patterns of the goats, with flowering herbs dominating during the wet season, a diversified group of species contributing during the transition, and very specific shrubs, usually bearers of dried pods or plants with delayed phenology, sustaining the individuals during the dry season. In general, leaf initiation and flowering were the most preferred phenological stages. The feeding behaviour appears to be unrelated to the protein content of the different phenological stages. Such close links between the feeding behaviour of ruminants and the phenological stages of plant communities have profound implications in range management, in meeting the nutritional budgets appropriate to the animals, and in the study of range-plant conservation aspects, particularly the evolution of plant populations under various intensities of stress.

The Course of Naturally Acquired Helminth Infections of Horses Given Regular Anthelmintic Treatment

Summary Three groups of 3 pony foals were grazed together on old established pasture, heavily contaminated with strongyle larvae. Two groups were treated each month with thiabendazole at dosages of 50 mg./kg. and 240 mg./kg. and the third group was kept undosed as a control. During 2 years of monthly observations, the peripheral eosinophil counts were similar in each group, irrespective of the anthelmintic treatment given. Further, there appeared to be a rhythm in the eosinophil counts, higher counts being recorded in the summer months and lower counts during the winter months. It is suggested that the eosinophil counts reflect the degree of exposure to infection and the subsequent larval systemic migration. There was no correlation between the eosinophil counts and the adult worm egg-producing population in the lumen of the intestines. The serum β-globulins were high in all animals at the beginning of the experiment, but in the treated groups a marked reduction occurred.